Pediatric Neurology Resident Johns Hopkins University Baltimore, Maryland
Rationale: Olfactory dysfunction has been well-documented in individuals with temporal lobe epilepsy, but its use in pre-surgical planning has yet to be examined. We assessed the role of pre-operative odor identification in mesial onset seizure localization utilizing stereoelectroencephalography (S-EEG) and MR-guided laser interstitial thermal therapy (MRgLiTT) outcome. Methods: We identified 30 patients who had typical seizures captured during S-EEG monitoring or MRgLiTT of mesial temporal structures (N= 17 S-EEG, N= 13 MRgLiTT); seizure onset zone was classified as 1) unilateral mesial seizure onset or 2) multifocal with unilateral mesial onset and non-mesial onset. Odor identification ability was assessed using the Sniffin’ Sticks Odor Identification Test (SS-OIT). Patients also completed measures of confrontation naming using the 60-item Boston Naming Test (BNT-60) and auditory-verbal learning and memory using the Hopkins Verbal Learning Test-Revised (HVLT-R). Results: Overall, patients with intractable focal epilepsy exhibited poor olfactory performance (Median [M]10.4, interquartile range [IQR] 9.4-11.8). Patients who were seizure free after MRgLiTT (N=10) had significantly worse odor identification scores (M 9, IQR 7-13) compared to patients who were not seizure free (M 13, IQR 12.5-15) with and without adjustment for age, sex, BNT-60 and HVLT scores. Of the 19 patients who underwent MRgLiTT, 10 patients (52.6%) were seizure free at last follow up (M 15 months, standard deviation [SD] 8.3). Receiver operating characteristic analysis revealed that SSOIT score of 12 was the ideal cutoff for predicting favorable seizure outcome (area under the curve [AUC]= 0.84 95% confidence interval [CI] .64-1.0); sensitivity was 88.9% and specificity was 78.9%, likelihood ratio of 2.9 of seizure freedom in patients who score < 12. Conclusions: Inter-ictal olfactory dysfunction is commonly seen in patients with intractable focal epilepsy. Our study is the first to demonstrate that the severity of olfactory dysfunction can help differentiate mesial versus non-mesial seizure onset and may be a novel pre-surgical biomarker to determine who may benefit from MRgLiTT. Funding: Please list any funding that was received in support of this abstract.: None. Click here to view image/table